1. Field of the Invention
The invention is related to the field of communications, and in particular, to converged service control for IMS networks and legacy networks.
2. Statement of the Problem
Intelligent networks (IN) and advanced intelligent networks (AIN) are service-independent telecommunications networks. An example of a wireline intelligent network is a Public Switched Telephone Network (PSTN), and examples of wireless intelligent networks are CDMA networks and GSM networks. Intelligent networks move the intelligence out of the switches to intelligent peripherals or network resources distributed throughout the network. This provides the network operator with the means to develop and control services more efficiently. Examples of services provided by intelligent networks include 800-number routing, abbreviated dialing, pre-paid services, Virtual Private Networks, notification and voice recognition services, etc. Wireless and wireline intelligent networks are referred to generally herein as legacy networks.
Other networks are being developed to provide advanced multimedia applications, such as IP Multimedia Subsystem (IMS) networks. As set forth in the 3rd Generation Partnership Project (3GPP), the IMS provides a common core network having access-agnostic network architecture for converged networks. Service providers are accepting this architecture in next generation network evolution. The IMS architecture is initially defined by the 3GPP to provide multimedia services to mobile subscribers over an Internet Protocol (IP) network. IP networks have become the most cost savings bearer network to transmit video, voice, and data. IMS uses the advantage of IP networks to provide multimedia services for IMS subscribers on an IMS platform. The signaling used within IMS networks is Session Initiation Protocol (SIP). IMS defines the standard SIP interface between application servers, the IMS core network (CSCF), the IMS subscriber, the IMS database (HSS), and IMS billing/charging elements. These standards can reduce the network integration costs and let the subscriber enjoy more stable services.
On the IMS platform, the traditional supplementary services, such as call forwarding, conferencing, and call waiting are available for IMS subscribers. Also, many new data services, such as instant messaging, video calls, video on wait, and web-based services, will also be available for the IMS subscribers.
Service providers that operate one or more legacy networks may also implement new IMS networks. FIG. 1 illustrates a network architecture 100 implementing both a legacy network 110 and an IMS network 130 in the prior art. Legacy network 110 includes a Mobile Switching Center (MSC) 111, an intelligent network Service Control Point (SCP) 112, an intelligent peripheral 113, a Short Message Service Center (SMSC) 114, and a Home Location Register (HLR) 115. IMS network 130 includes a Call Session Control Function (CSCF) 131, an Online Charging System (OCS) 132, a media server 133, a Charging Gateway Function (CGF) 134, a Charging Data Function (CDF) 135, an IMS gateway function 136, and a Service Control Application Server (AS) 137. SCP 112, MSC 111, OCS 132, and CGF 134 communicate with billing domain 140. Billing domain 140 typically comprises Call Detail Record and Charging Data Record post-processing systems such as the operator's billing system or billing mediation device. Media gateway 142 may terminate bearer channels from a switched circuit network and media streams from a packet network. Media gateway 142 may support media conversion, bearer control, and payload processing, such as encoding/decoding, echo canceling, or a conference bridge.
MSC 111 is a switching element for legacy network 110. SCP 112 provides service control functions, account management, charging and rating functions, and notification functions for legacy network 110. Intelligent peripheral 113 is a physical entity that implements Intelligent Network specialized resource functions, such as voice announcements. SMSC 114 is adapted to transfer short message notification to a mobile subscriber via Short Message Delivery Point-to-Point format. HLR 115 is responsible for managing mobile subscribers. HLR 115 stores and manages subscriber information, and part of the mobile information that allows incoming calls to be routed to the mobile subscriber.
Service control in legacy network 110 is traditionally performed in SCP 112. As an example, assume MSC 111 receives signaling for a call from a mobile subscriber (not shown). If the call requires intelligent services, such as for a pre-paid call, MSC 111 queries SCP 112 for service control. SCP 112 includes a charging and rating function that determines whether the mobile subscriber has units left in his/her account to place the call, requests units for the call, etc. If an announcement is needed, such as to inform the mobile subscriber of the number of minutes left in his/her account, then SCP 112 may instruct intelligent peripheral 113 to play an announcement to the mobile subscriber. If a text message is needed, then SCP 112 may instruct SMSC 114 to transmit a text message to the mobile subscriber. After providing the needed services, SCP 112 responds to MSC 111 with routing instructions for the call. SCP 112 also reports to billing domain 140 regarding charging for the call.
In IMS network 130, CSCF 131 serves as a centralized routing engine, policy manager, and policy enforcement point to facilitate the delivery of multiple real-time applications using IP transport. OCS 132 provides online charging for IMS network 130. Online charging is a process where charging information for network resource usage is collected concurrently with resource usage, but authorization of the network resource usage must be obtained by the network prior to the actual resource usage. CGF 134 and CDF 135 provide offline charging for IMS network 130. Offline charging is a process where charging information for network resource usage is collected concurrently with the resource usage. At the end of this process, Charging Detail Records (CDRs) are generated and transferred to billing domain 140. Media server 133 provides a wide range of functions for multimedia resources, including provision of resources, mixing of incoming media streams, sourcing media streams (for multimedia announcements), and processing of media streams. IMS gateway 136 is an interface between CSCF 131 and OCS 132. Service control AS 137 provides service control as desired.
Service control in IMS network 130 is performed in service control AS 137 and IMS gateway 136. As an example, assume CSCF 131 receives a SIP INVITE message to initiate a call session from a subscriber. If the call is a pre-paid call, then CSCF 131 transmits SIP messages to IMS gateway 136 for service control. IMS gateway 136 and/or AS 137 queries OCS 132 for charging and rating for the call. If an announcement is need, such as to inform the mobile subscriber of the number of minutes left in his/her account, then IMS gateway 136 and/or AS 137 may instruct media server 133 to play an announcement to the mobile subscriber. OCS 132 also reports to billing domain 140 regarding charging for the call.
FIG. 2 illustrates a charging architecture 200 suggested by the 3GPP in the prior art. For IMS network 130, CSCF 131 (labeled S-CSCF in FIG. 2) connects to IMS gateway 136 through an ISC interface and IMS gateway 136 connects to OCS 132 through the Ro interface for online charging (see also FIG. 1). CSCF 131 connects to CDF 135 through the Rf interface (such as through the P/I CSCF) for offline charging. For legacy network 110, MSC 111 may connect to OCS 132 through a CAMEL Application Part (CAP) interface for online charging (in GSM networks). MSC 111 may connect to billing domain 140 through a Bc interface. Other features and connections of charging architecture 200 are known to those familiar with the 3GPP architecture and will not be discussed in detail.
One problem for services providers is having separate service control and separate charging when implementing both legacy networks and IMS networks. If new services and new service control are implemented, the separate service control functions in the different networks have to be updated. Further, if charging or rating functions need to be updated, the separate charging functions of the different networks need to be updated. Further, if there are separate service controls, the services will generate charging data records (CDR) in different formats, which will cause the billing domain to have to consolidate and reformat the CDRs. Updating and maintaining separate service control functions and separate charging functions can be costly and time consuming.